The WB1400 was the main communication system for all posts. The Tele-Talk was linked via the little brown box in the bottom left of the picture. The fatal flaw with this system was the fact that this required telephone lines to transmit the information. In the event of a nuclear blast, phone lines were exceptionally vulnerable. This was all about the percentages game though. Whilst a nuclear attack would hit 6 or 7 areas on mainland Britain, the vast majority of the telephone network would continue to work, transmitting the vital data. Posts in the affected blast areas would have to manually delivered their respective readings to their allotted Master Posts for transmission across the radio via the Burndept BE 525. Naturally, you would be exposed to radiation as you travelled the 8 to 10 miles to your master post.